package com.bao.examples.jsse;

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/**
 * A SSLEngine usage example which simplifies the presentation
 * by removing the I/O and multi-threading concerns.
 *
 * The demo creates two SSLEngines, simulating a client and server.
 * The "transport" layer consists two ByteBuffers:  think of them
 * as directly connected pipes.
 *
 * Note, this is a *very* simple example: real code will be much more
 * involved.  For example, different threading and I/O models could be
 * used, transport mechanisms could close unexpectedly, and so on.
 *
 * When this application runs, notice that several messages
 * (wrap/unwrap) pass before any application data is consumed or
 * produced.  (For more information, please see the SSL/TLS
 * specifications.)  There may several steps for a successful handshake,
 * so it's typical to see the following series of operations:
 *
 *	client		server		message
 *	======		======		=======
 *	wrap()		...		ClientHello
 *	...		unwrap()	ClientHello
 *	...		wrap()		ServerHello/Certificate
 *	unwrap()	...		ServerHello/Certificate
 *	wrap()		...		ClientKeyExchange
 *	wrap()		...		ChangeCipherSpec
 *	wrap()		...		Finished
 *	...		unwrap()	ClientKeyExchange
 *	...		unwrap()	ChangeCipherSpec
 *	...		unwrap()	Finished
 *	...		wrap()		ChangeCipherSpec
 *	...		wrap()		Finished
 *	unwrap()	...		ChangeCipherSpec
 *	unwrap()	...		Finished
 */

import javax.net.ssl.*;
import javax.net.ssl.SSLEngineResult.*;
import java.io.*;
import java.security.*;
import java.nio.*;

public class SSLEngineSimpleDemo {

    /*
     * Enables logging of the SSLEngine operations.
     */
    private static boolean logging = true;

    /*
     * Enables the JSSE system debugging system property:
     *
     *     -Djavax.net.debug=all
     *
     * This gives a lot of low-level information about operations underway,
     * including specific handshake messages, and might be best examined
     * after gaining some familiarity with this application.
     */
    private static boolean debug = false;

    private SSLContext sslc;

    private SSLEngine clientEngine;	// client Engine
    private ByteBuffer clientOut;	// write side of clientEngine
    private ByteBuffer clientIn;	// read side of clientEngine

    private SSLEngine serverEngine;	// server Engine
    private ByteBuffer serverOut;	// write side of serverEngine
    private ByteBuffer serverIn;	// read side of serverEngine

    /*
     * For data transport, this example uses local ByteBuffers.  This
     * isn't really useful, but the purpose of this example is to show
     * SSLEngine concepts, not how to do network transport.
     */
    private ByteBuffer cTOs;		// "reliable" transport client->server
    private ByteBuffer sTOc;		// "reliable" transport server->client

    /*
     * The following is to set up the keystores.
     */
    private static String keyStoreFile = "testkeys";
    private static String trustStoreFile = "testkeys";
    private static String passwd = "passphrase";

    /*
     * Main entry point for this demo.
     */
    public static void main(String args[]) throws Exception {
	if (debug) {
	    System.setProperty("javax.net.debug", "all");
	}

	SSLEngineSimpleDemo demo = new SSLEngineSimpleDemo();
	demo.runDemo();

	System.out.println("Demo Completed.");
    }

    /*
     * Create an initialized SSLContext to use for this demo.
     */
    public SSLEngineSimpleDemo() throws Exception {

	KeyStore ks = KeyStore.getInstance("JKS");
	KeyStore ts = KeyStore.getInstance("JKS");

	char[] passphrase = "passphrase".toCharArray();

	ks.load(new FileInputStream(keyStoreFile), passphrase);
	ts.load(new FileInputStream(trustStoreFile), passphrase);

	KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
	kmf.init(ks, passphrase);

	TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509");
	tmf.init(ts);

	SSLContext sslCtx = SSLContext.getInstance("TLS");

	sslCtx.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);

	sslc = sslCtx;
    }

    /*
     * Run the demo.
     *
     * Sit in a tight loop, both engines calling wrap/unwrap regardless
     * of whether data is available or not.  We do this until both engines
     * report back they are closed.
     *
     * The main loop handles all of the I/O phases of the SSLEngine's
     * lifetime:
     *
     *     initial handshaking
     *     application data transfer
     *     engine closing
     *
     * One could easily separate these phases into separate
     * sections of code.
     */
    private void runDemo() throws Exception {
	boolean dataDone = false;

	createSSLEngines();
	createBuffers();

	SSLEngineResult clientResult;	// results from client's last operation
	SSLEngineResult serverResult;	// results from server's last operation

	/*
	 * Examining the SSLEngineResults could be much more involved,
	 * and may alter the overall flow of the application.
	 *
	 * For example, if we received a BUFFER_OVERFLOW when trying
	 * to write to the output pipe, we could reallocate a larger
	 * pipe, but instead we wait for the peer to drain it.
	 */
	while (!isEngineClosed(clientEngine) ||
		!isEngineClosed(serverEngine)) {

	    log("================");

	    clientResult = clientEngine.wrap(clientOut, cTOs);
	    log("client wrap: ", clientResult);
	    runDelegatedTasks(clientResult, clientEngine);

	    serverResult = serverEngine.wrap(serverOut, sTOc);
	    log("server wrap: ", serverResult);
	    runDelegatedTasks(serverResult, serverEngine);

	    cTOs.flip();
	    sTOc.flip();

	    log("----");

	    clientResult = clientEngine.unwrap(sTOc, clientIn);
	    log("client unwrap: ", clientResult);
	    runDelegatedTasks(clientResult, clientEngine);

	    serverResult = serverEngine.unwrap(cTOs, serverIn);
	    log("server unwrap: ", serverResult);
	    runDelegatedTasks(serverResult, serverEngine);

	    cTOs.compact();
	    sTOc.compact();

	    /*
	     * After we've transfered all application data between the client
	     * and server, we close the clientEngine's outbound stream.
	     * This generates a close_notify handshake message, which the
	     * server engine receives and responds by closing itself.
	     *
	     * In normal operation, each SSLEngine should call
	     * closeOutbound().  To protect against truncation attacks,
	     * SSLEngine.closeInbound() should be called whenever it has
	     * determined that no more input data will ever be
	     * available (say a closed input stream).
	     */
	    if (!dataDone && (clientOut.limit() == serverIn.position()) &&
		    (serverOut.limit() == clientIn.position())) {

		/*
		 * A sanity check to ensure we got what was sent.
		 */
		checkTransfer(serverOut, clientIn);
		checkTransfer(clientOut, serverIn);

		log("\tClosing clientEngine's *OUTBOUND*...");
		clientEngine.closeOutbound();
		// serverEngine.closeOutbound();
		dataDone = true;
	    }
	}
    }

    /*
     * Using the SSLContext created during object creation,
     * create/configure the SSLEngines we'll use for this demo.
     */
    private void createSSLEngines() throws Exception {
	/*
	 * Configure the serverEngine to act as a server in the SSL/TLS
	 * handshake.  Also, require SSL client authentication.
	 */
	serverEngine = sslc.createSSLEngine();
	serverEngine.setUseClientMode(false);
	serverEngine.setNeedClientAuth(true);

	/*
	 * Similar to above, but using client mode instead.
	 */
	clientEngine = sslc.createSSLEngine("client", 80);
	clientEngine.setUseClientMode(true);
    }

    /*
     * Create and size the buffers appropriately.
     */
    private void createBuffers() {

	/*
	 * We'll assume the buffer sizes are the same
	 * between client and server.
	 */
	SSLSession session = clientEngine.getSession();
	int appBufferMax = session.getApplicationBufferSize();
	int netBufferMax = session.getPacketBufferSize();

	/*
	 * We'll make the input buffers a bit bigger than the max needed
	 * size, so that unwrap()s following a successful data transfer
	 * won't generate BUFFER_OVERFLOWS.
	 *
	 * We'll use a mix of direct and indirect ByteBuffers for
	 * tutorial purposes only.  In reality, only use direct
	 * ByteBuffers when they give a clear performance enhancement.
	 */
	clientIn = ByteBuffer.allocate(appBufferMax + 50);
	serverIn = ByteBuffer.allocate(appBufferMax + 50);

	cTOs = ByteBuffer.allocateDirect(netBufferMax);
	sTOc = ByteBuffer.allocateDirect(netBufferMax);

	clientOut = ByteBuffer.wrap("Hi Server, I'm Client".getBytes());
	serverOut = ByteBuffer.wrap("Hello Client, I'm Server".getBytes());
    }

    /*
     * If the result indicates that we have outstanding tasks to do,
     * go ahead and run them in this thread.
     */
    private static void runDelegatedTasks(SSLEngineResult result,
	    SSLEngine engine) throws Exception {

	if (result.getHandshakeStatus() == HandshakeStatus.NEED_TASK) {
	    Runnable runnable;
	    while ((runnable = engine.getDelegatedTask()) != null) {
		log("\trunning delegated task...");
		runnable.run();
	    }
	    HandshakeStatus hsStatus = engine.getHandshakeStatus();
	    if (hsStatus == HandshakeStatus.NEED_TASK) {
		throw new Exception(
		    "handshake shouldn't need additional tasks");
	    }
	    log("\tnew HandshakeStatus: " + hsStatus);
	}
    }

    private static boolean isEngineClosed(SSLEngine engine) {
	return (engine.isOutboundDone() && engine.isInboundDone());
    }

    /*
     * Simple check to make sure everything came across as expected.
     */
    private static void checkTransfer(ByteBuffer a, ByteBuffer b)
	    throws Exception {
	a.flip();
	b.flip();

	if (!a.equals(b)) {
	    throw new Exception("Data didn't transfer cleanly");
	} else {
	    log("\tData transferred cleanly");
	}

	a.position(a.limit());
	b.position(b.limit());
	a.limit(a.capacity());
	b.limit(b.capacity());
    }

    /*
     * Logging code
     */
    private static boolean resultOnce = true;

    private static void log(String str, SSLEngineResult result) {
	if (!logging) {
	    return;
	}
	if (resultOnce) {
	    resultOnce = false;
	    System.out.println("The format of the SSLEngineResult is: \n" +
		"\t\"getStatus() / getHandshakeStatus()\" +\n" +
		"\t\"bytesConsumed() / bytesProduced()\"\n");
	}
	HandshakeStatus hsStatus = result.getHandshakeStatus();
	log(str +
	    result.getStatus() + "/" + hsStatus + ", " +
	    result.bytesConsumed() + "/" + result.bytesProduced() +
	    " bytes");
	if (hsStatus == HandshakeStatus.FINISHED) {
	    log("\t...ready for application data");
	}
    }

    private static void log(String str) {
	if (logging) {
	    System.out.println(str);
	}
    }
}
